The long-term objective of this proposal is a better understanding of fundamental biological processes in human eyes that play a role in protecting ocular tissues from the everyday exposure to potentially damaging reactive oxygen species. An inability to detoxify free radicals can lead to "wear and tear" and tissue damage such as that associated with aging and with age- related macular degeneration. Clinical investigations suggest that oral administration of antioxidants can retard vision loss from macular degeneration in at least some persons. Investigations at the cellular and molecular levels are proposed to learn more about chorioretinal antioxidant system elements, including zinc, catalase and metallothionein (MT) with the following specific aims: (1) to determine the interrelations of zinc, MT, and catalase in vitro and in vivo in providing the RPE protection from oxidative stress as reflected by changes in lipid peroxidation products; (2) to investigate the regulation of MT in the response of the RPE to the oxidative stress of ROS phagocytosis and exposure to increased reactive oxygen species; and (3) to determine the effects of zinc and oxidative stress on the formation of glycoconjugates by the RPE. Use will be made of isolated human donor RPE tissue, cultured human RPE cells, and an in vivo rat model of zinc deficiency. These studies will increase understanding of how molecules related to the antioxidant economy of RPE are regulated, and how they may affect other cellular functions, including the synthesis and degradation of Bruch's membrane. Understanding these basic cellular events is crucial to development of diagnostic and prognostic tools to treat the symptoms of macular degeneration.